nondisjunction

nondisjunction

[non″dis-jungk´shun]

failure either of two homologous chromosomes to pass to separate cells during the first meiotic division, or of the two chromatids of a chromosome to pass to separate cells during mitosis or during the second meiotic division. As a result, one daughter cell has two chromosomes or two chromatids, and the other has none. If this happens during meiosis, an aneuploid individual (for example, a child with Down syndrome) may develop following fertilization.

Nondisjunction. Normal meiosis (A) is contrasted with failure of homologous chromosomes to separate in meiosis I (B) or of sister chromatids to separate in meiosis II (C). From Dorland's, 2000.

non·dis·junc·tion

(non'dis-jŭnk'shŭn), [MIM*257300]

Failure of one or more pairs of chromosomes to separate at the meiotic stage of karyokinesis, with the result that both chromosomes are carried to one daughter cell and none to the other.

nondisjunction

/non·dis·junc·tion/ (-dis-junk´shun) failure either of two homologous chromosomes to pass to separate cells during the first meiotic division, or of the two chromatids of a chromosome to pass to separate cells during mitosis or during the second meiotic division. As a result, one daughter cell has two chromosomes or two chromatids, and the other has none.

Nondisjunction. Normal meiosis (A) is contrasted with failure of homologous chromosomes to separate in meiosis I (B) or of sister chromatids to separate in meiosis II (C).

nondisjunction

(nŏn′dĭs-jŭngk′shən)

n.

The failure of paired chromosomes or sister chromatids to separate and go to different cells during meiosis.

non′dis·junc′tion·al adj.

nondisjunction

[-disjungk′chən]

Etymology: L, non + disjungere, to disjoint

failure of homologous pairs of chromosomes to separate during the first meiotic division or of the two chromatids of a chromosome to split during anaphase of mitosis or the second meiotic division. The result is an abnormal number of chromosomes in the daughter cells. Compare disjunction. See also monosomy,trisomy.

non·dis·junc·tion

(non'dis-jŭngk'shŭn)

Failure of one or more pairs of chromosomes to separate at the meiotic stage of karyokinesis, with the result that both chromosomes are carried to one daughter cell and none to the other.

NONDISJUNCTION

nondisjunction

(nŏn″dĭs-jŭnk′shŭn)

The failure of a pair of chromosomes to separate during meiosis, allowing one daughter cell to have two chromosomes and the other to have none.

nondisjunction

failure (1) of two homologous chromosomes to pass to separate cells during the first division of meiosis, or (2) of the two chromatids of a chromosome to pass to separate cells during mitosis or during the second meiotic division. As a result, one daughter cell has two chromosomes or two chromatids, and the other has none. Death of the fetus or chromosomal anomalies may result.

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